This invention relates to the cleaning of teeth, and, in particular, to a head or handpiece for a cleaner which cleans by abrading a tooth surface with soluble abrasive particles in the presence of liquid. It is particularly directed to a device known to dentists and hygienists as an airpolisher. Airpolishers use air, abrasive, and liquid, combined in various ways, to clean and polish teeth, perform root planing, and reduce microbial count prior to oral surgery.
The use of a spray of soluble abrasive particles in the presence of a liquid to clean teeth has long been known. Several approaches have been used.
In some approaches, a stream of water in which abrasive is partially or completely dissolved is directed at the teeth. An example of such an approach is Arnold, U.S. Pat. No. 4,214,871. Although, as pointed out by Arnold, the use of liquid as the carrier for the soluble particles has the advantages over gas that it does not cool as it expands through a nozzle, that it has a residual flushing effect, and that the pressure does not have to be as great because of the higher density of liquids over gases, it is not an entirely effective way to clean and polish teeth. It also does not permit easy adjustment of the degree of cleaning performed.
Other approaches are exemplified by Gallant, U.S. Pat. Nos. 4,174,571 and 4,412,402. These patents use air as a carrier gas for the soluble abrasive; they direct the air/abrasive stream toward the tooth, and direct a separate stream of water toward the tooth.
In the former ('571) patent, the water stream is in the form of one or more jets arranged so that the water will impinge upon the surface being treated very close to or overlapping with the target area for the air/abrasive stream. When the water stream joins the air/abrasive stream, a slurry is formed and the cleaning or abrasion is effected, at least in part, by means of such slurry. Using this device, a hygienist must hold the head a certain distance from the tooth for the abrasive and water to properly mix at the tooth. Thus this cleaner is "technique sensitive." If the head is held too close to the tooth, the abrasive builds up in intradental spaces, reducing the effectiveness of the cleaner. Further, if the head is held still, the abrasive particles form a pile in the middle of the water curtain and the water flows around the abrasive pile. Thus, to clean the tooth effectively, the hygienist must continuously move the head in the patient's mouth at a fixed distance a few millimeters from the tooth surface. The device is therefore difficult to use for cleaning fine crevices or around orthodontal appliances. The device of the patent is also bulky and therefore difficult to use in the mouth of a patient. This drawback has been reduced somewhat in a commercial device made according to the patent, by forming a tip of concentric tubes. The device also requires a high air pressure which may cause discomfort to the patient and damage to soft tissue, such as gums, particularly if the nozzle is held directly against the tissue. It also produces a substantial aerosol overspray which may deposit throughout the operatory and is both an annoyance and a potential hazard.
In the latter ('402) patent, the discharge nozzle has a central orifice for the air/abrasive stream and an annular water orifice extending around and a short distance beyond the central orifice. Instead of delivering the water as a jet, the water is released as a non-pressurized flow and is caused to join (at least to some degree) the air/abrasive stream under the influence of the induction effect of the air/abrasive jet on the way to the tooth. Even though some of the abrasive may be dry when it impinges the tooth, no cloud of dry abrasive particles is produced because it is contained by the water curtain. Because mixing of the water with the air/abrasive stream occurs on the way to the tooth, the head must still be held a proper distance from the tooth, although it is somewhat less technique sensitive than the device of the '571 patent. Although this approach was intended to solve some of the problems of the '571 patent, it produced problems of its own, particularly clogging of the device. Clogging of the device may occur in normal operation, and causes major problems when the hygienist touches the nozzle to the patient's tooth or gum, thereby causing water to back up into the air/abrasive line. As a result, this device was not commercially successful.
Another approach is disclosed in Edel et al, U.S. Pat. No. 4,595,365. In this device, a pressurized air/abrasive stream and a pressurized water stream are mixed in a chamber in the head to provide a homogeneous mixture, and a single stream of this mixture exits the head. This approach has the virtue of being far less technique sensitive than the approaches of the Gallant patents. The head is bulky, however, because water is brought into the head from the side and because of the size of the mixing chamber. Moreover, the large volume and pressure of the water stream makes it difficult to control the correct air/abrasive/water mixture. It also produces a good deal of overspray in the patient's mouth and throughout the operatory. It also creates a potential problem of clogging, which becomes a very real problem should the hygienist accidentally block the outlet.
Yet another approach is shown in Meller, U.S. Pat. No. 4,776,794, in which a water/abrasive mixture is carried by a head and injected into an air stream. This approach requires a bulky head to carry the water/abrasive mixture, is not easily controlled, and requires the use of abrasive materials which are not readily soluble in water.
All of the prior art heads and methods also produce a spray which is not well focused and therefore are not well suited to cleaning small fissures or other small areas of a tooth or a root.